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GeTe-based alloys have been studied as promising TE materials in the mid-temperature range, as a lead-free alternate to PbTe due to their non-toxicity. Our previous study on GeTe1-xIx revealed that I-doping increases lattice anharmonicity and decreases the structural phase transition temperature, consequently enhancing thermoelectric performance. Our current work elucidates the synergistic interplay between band convergence and lattice softening, resulting in an enhanced thermoelectric performance for Ge1-ySbyTe0.9I0.1 (y=0.10, 0.12, 0.14, and 0.16). Sb doping in GeTe0.9I0.1 serves a double role: firstly, it leads to lattice softening, thereby reducing lattice thermal conductivity; secondly, it promotes a band convergence, thus a higher valley degeneracy. The presence of lattice softening is corroborated by an increase in the internal strain ratio observed in XRD patterns. Doping also introduces phonon scattering centers, further diminishing lattice thermal conductivity. Additionally, variations in the electronic band structure are indicated by an increase in density of state effective mass and a decrease in carrier mobility with Sb concentration. Besides, Sb doping
optimizes the carrier concentration efficiently. Through a two-band modeling and electronic band structure calculations, the valence band convergence due to Sb doping can be confirmed. Specifically, the energy difference between valence bands progressively narrows upon Sb doping in Ge1-ySbyTe0.9I0.1 (y=0, 0.02, 0.05, 0.10, 0.12, 0.14, and 0.16). As a culmination of these effects, we have achieved a significant enhancement in 𝑧𝑇 for Ge1-ySbyTe0.9I0.1 (y=0.10, 0.12, 0.14, and 0.16) across the entire range of measured temperatures. Notably, the sample with y=0.12 exhibits the highest 𝑧𝑇 value of 1.70 at 723K.

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  This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Applied Materials & Interfaces, copyright © 2024 American Chemical Society after peer review. To access the final edited and published work see https://doi.org/10.1021/acsami.4c09683

Keyword: thermoelectric

Date published: 2024-09-04

Publisher: American Chemical Society (ACS)

Journal:

• ACS Applied Materials & Interfaces (ISSN: 19448252) vol. 16 issue. 35 p. 46363-46373

Funding:

• JST-Mirai Program JPMJMI19A1
• National Research Foundation of Korea NRF-2022M3C1A3091988

Manuscript type: Author's version (Submitted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4801

First published URL: https://doi.org/10.1021/acsami.4c09683

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Updated at: 2024-10-07 14:41:35 +0900

Published on MDR: 2024-10-07 14:41:35 +0900